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ABSTRACT
Beneficial effects of redtop residues on yields of potatoes grown on a Bridgehampton silt loam were correlated with increased soil aggregation; particularly with larger aggregates. There was an accumulation of carbon in all aggregates studied. However, the quantity does not appear to be related consistently to degree of aggregation. Analyses of total soil and aggregates (> 1 mm., 1 to 0.25 mm., 0.25 to 1 mm.) for microbial gums, polyuronides and acid hydrolyzable polyhexose carbohydrates indicate a similarity in quantities of these constituents as functions of organic carbon. Generally, somewhat wider C/N ratios (13:1) were found in larger aggregates where redtop was included, compared with smaller sizes (11:1). Extraction of organic matter with 0.5N NaOH and neutral 0.1M pyrophosphate indicates similar humic materials loosely held by this silt soil regardless of source. About 6 to 9% of the total carbon found in aggregates could be consistently accounted for as acid-hydrolyzable carbohydrate. There was little difference in this fraction due to rotation or size of aggregate.
1 Contribution No. 1021 of the Rhode Island Agr. Exp. Sta., Kingston. Presented before Div. IV, Soil Science Society of America, Chicago, Ill., Dec. 8, 1960. This project was supported in part by funds from a regional research project in cooperation with other experiment stations of the Northeast under Project N. E. 11, Soil Structure Problems in Northeastern Agriculture.
2 Professor of Agricultural Chemistry. Field experiments were planned and conducted by the Agronomy Department.
Received for publication February 15, 1961. Accepted for publication February 17, 1961.
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